Ultra-sharp nanoprobes can offer many applications in the areas of high-efficiency field emission flat panel displays, biochemistry (biochemical sensing), biomimetics, electronics, atomic/scanning probe microscopy, scanning tunneling microscopy, nanolithography, optics, and nanoimprinting.
The most important nanoprobes parameters for some of the above-cited applications can include the apex size, the probe location and the probe shape. Nanoprobes can be fabricated from a multitude of materials including silicon, silica, metal, polymer, and carbon nanotube. For atomic force microscopy (AFM) applications, the radius of curvature of the probe end is the point of contact between the probe and the sample, and the radius of curvature can be responsible for the lateral distortion that is seen in the resulting AFM images. In order to get clearer, more accurate pictures, the AFM probe radius should be as small as possible. Also, the probe's access to the depths of the sample and the microscope depth of field can be determined and can be limited by the shape of the probe's body.
Nanoprobe fabrication is fast becoming an attractive research field in nanoengineering. Many groups are trying to find ways of minimizing the probe radius, and many groups are also exploring methods of engineering the shape of the nanoprobe body. The current state of the art in nanoprobes fabrication can often rely on techniques that utilize elaborate precursor chemicals, catalysts, vacuum conditions, or equipment, and any combination thereof. To realize their ultimate potential, synthesized nanoprobes may require simpler fabrication techniques that can allow for control over the final nanomorphology of the nanoprobe.
One such nanoprobe fabrication technique can be the Bosch process, which alternates repeatedly between two modes to achieve nearly vertical structures. The first mode can be a standard, nearly isotropic plasma etch. The plasma contains some ions, which attack the wafer from a nearly vertical direction. Sulfur hexaflouride SF6 is often used for silicon. The second mode can be deposition of a chemically inert passivation layer. For instance, C4F8 source gas can yield a substance similar to a Teflon® material. Each mode can last for several seconds. The passivation layer can protect the entire substrate from further chemical attack and prevents further etching. However, during the etching phase, the directional ions that bombard and etch the substrate also attack the passivation layer at the bottom of the trench (but not along the sides). The directional ions can collide with the passivation layer and can sputter portions of the passivation layer off, which can expose the substrate to the chemical etchant. Further, these etch/deposit steps are repeated many times over, which can result in a large number of very small isotropic etch steps taking place only at the bottom of the etched pits.
The Bosch process described above can be time consuming and it can result in spiral shaped nanoprobes. Other alternative fabrication methods can include plasma etching with Cl2/HBr or anisotropic wet etching with KOH. The Cl2/HBr etch method can require nanoscale patterning using electron beam lithography prior to the etching process, which can be time consuming and expensive. Also, the delicate processing care required for these methods can result in low production yield. Anisotropic wet etching is a relatively simple fabrication method, but this method can typically result in pyramidal shape structures, which are not tall, and which lack very sharp ends. Thus, this method of etching can result in nanoprobes with limited effectiveness.
In view of the above, it can be an object of the present invention to provide a method for manufacturing ultra-sharp nanoprobes which can be used more effectively for AFM applications. Another object of the present invention can be to provide a method for manufacturing ultra-sharp nanoprobes, which can result in a relatively high yield of nanoprobes, when compared to the prior art. Still another object of the present invention is to provide a method for manufacturing ultra-sharp nanoprobes that uses low temperature deposition techniques to fabricate the nanoprobes. Another object of the present invention to provide a method for manufacturing ultra-sharp nanoprobes that take advantage of non-uniform cladding “defects” to fabricate the nanoprobe. Yet another object of the present invention is to provide a method for manufacturing ultra-sharp nanoprobes which is easy to manufacture, that is inexpensive, and that is easy to use.